QSensorManager: iterate over const

Avoid unnecessary detaches and overhead from ref-count checking by
iterating over const containers.

This addresses all style violations reported by Axivion for the Qt
Sensors module. All changes are trivial, so picking back to non-strict
branches to avoid future conflicts.

Axivion-Id: qt_Add-ons_qtsensors_dev_linux:SV89
Axivion-Id: qt_Add-ons_qtsensors_dev_linux:SV90
Axivion-Id: qt_Add-ons_qtsensors_dev_linux:SV91
Axivion-Id: qt_Add-ons_qtsensors_dev_linux:SV92
Fixes: QTBUG-146064
Pick-to: 6.12 6.11 6.8
Change-Id: If37b9255330fa6445e2db68abc1135cf4fd6bb48
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>